This invention relates to a plasma fuel converter and more particularly to a low power compact plasma fuel converter employing high voltage and low current.
Plasma fuel converters such as plasmatrons reform hydrocarbons to produce a hydrogen rich gas. DC arc plasmatrons have received particular attention in the prior art. See, for example, U.S. Pat. Nos. 5,425,332 and 5,437,250. DC arc plasmatrons typically operate at low voltage and high current. By operating at high currents and lower voltages, the arc current is high enough that precautions are required to minimize electrode erosion and even melting. High flow rates of cooling water are required to keep the erosion in check. Air flow is required to simultaneously center the discharge on the cathode tip (made of hafnium or other specialized material, embedded in a copper plug) and to move the root of the arc at the anode to minimize erosion at the anode. A constriction is also required to increase the impedance of the discharge (i.e., to operate at high voltages and lower currents than free-flowing arcs). The air flows and the constriction are likely to require operation at elevated pressure (as much as 0.5 bar above ambient pressure), and thus a compressor is likely to be required. Even with these precautions, it is often difficult to extend the lifetime of the electrodes beyond approximately 1,000 hours of operation.
DC plasmatrons also require relatively sophisticated power supplies for stabilization of the arc discharge. Further, DC plasmatrons have a limited capability for low power operation. In some reforming applications, the minimum operating power can be significantly greater than needed resulting in unnecessary power loss. DC arc plasmatrons are typically operated at power levels of one kilowatt or more.
It is therefore desirable to have a plasma fuel converter that does not require a compressor or a sophisticated power supply for stabilization of the arc discharge. It is also desirable to have a plasma fuel converter having longer electrode life and with a capability of lower power operation when lower flow rates of hydrogen rich gas are required.